Vine plants, for example tomato plants are commonly planted in rows in a greenhouse environment. Strings are typically suspended from spools supported on an overhead structure of the greenhouse such that the vine plants are permitted to grow upwardly along the string upon which they are supported. As the plant grows to the top of the string, the string is unwound from the spool and the spool is displaced horizontally in the direction of the rows of plants so that the vine plants are effectively layered on top of one another along the growing media supporting the plants in the direction of the rows.
U.S. Pat. Nos. 6,928,772 by Eai et al. and 4,254,579 by Flynn disclose examples of devices for supporting and training vine plants, such as tomatoes and the like. In each instance the spools from which the strings are suspended to support the vine plants respectively thereon must be individually and manually unwound as well as manually displaced along the row independently of one another as the vine plants are layered. The process of layering the vine plants is accordingly very labour intensive, consuming considerable time and effort, while also requiring dangerous use of scissor-lift carts that are being moved about frequently through a greenhouse environment.